Humans are exposed to nitroheterocyclic compounds through extensive use in medicine and industry; these chemicals are metabolically 'activated' to toxic, DNA damaging and in many cases, tumorigenic agents. We will attempt to determine the relationship between drug 'activation', DNA damage, mutagenicity and transforming ability of selected nitroheterocycles. Specifically, we will determine whether the electronegativity (reactivity) of these chemicals, as reported in the literature, is correlated with their ability to damage DNA, as measured by hydroxylapatite chromatography, their mutagenicity in bacterial tester strains, or their ability to transform cultured C3H/10T1/2 mammalian cells. In addition, we intend to determine whether the amount of nitrogen-induced DNA damage or its rate of repair differs in the specific target organ for tumor production, and further, whether this damage is due solely to metabolic activation in the target tissue or to transfer of 'activated' intermediates of nitrofuran metabolism.